1. Field of the Invention
The present invention relates to a compressor, and in particular to an apparatus and a method for controlling operation of a compressor which is capable of operating a compressor with an optimum efficiency by using a current and a voltage generated in a compressor.
2. Description of the Prior Art
Generally, because a linear compressor does not include a crankshaft converting a rotation motion into a linear motion, the linear compressor shows a less resistance loss than a resistance loss in a general compressor, accordingly the linear compressor is superior to the general compressor in a compressing efficiency aspect.
When the linear compressor is used for a refrigerator or an air conditioner, a freezing capacity of the refrigerator or the air conditioner can be controlled by varying a compressing ratio of the linear compressor by varying a voltage applied to the linear compressor. The above-mentioned linear compressor will be described with reference to the accompanying FIG. 1.
FIG. 1 is a block diagram illustrating a construction of an apparatus for controlling a linear compressor.
As depicted in FIG. 1, the apparatus for controlling operation of the linear compressor includes a linear compressor 13 varying an internal stroke (not shown) by being inputted a voltage supplied to an internal motor according to a stroke reference value and adjusting a freezing capacity by moving an internal piston up and down, a voltage detecting unit 14 detecting a voltage generated in the linear compressor 13 according to the variation of the stroke, a current detecting unit 14 detecting a voltage generated in the linear compressor 13 according to the variation of the stroke, a microcomputer 15 calculating a stroke by using the voltage detected from the voltage detecting unit 14 and the current detected from the current detecting unit 12, comparing the calculated stroke with a stroke reference value and outputting a switching control signal according to the comparison result, and a power supplying unit 11 supplying a stroke voltage to the linear compressor 13 by transmitting intermittently AC power to the linear compressor with an internal triac TrI according to the switching control signal outputted from the microcomputer 15. Hereinafter, the operation of the apparatus for controlling the linear compressor will be described in detail.
First, the linear compressor 13 varies the stroke by being inputted a voltage supplied to the motor according to the stroke reference value set by a user and adjusts a freezing capacity by moving the piston up and down according to the stroke. Herein, the stroke means a distance in which the piston of the compressor 13 moves while performing a reciprocating motion.
The triac TrI of the power supplying unit 11 has a longer turn on cycle according to the switching control signal outputted from the microcomputer 15, and the AC power is supplied to the linear compressor 31 while the turn on cycle of the triac TrI is lengthened, accordingly the linear compressor operates 31. Herein, the voltage detecting unit 14 and the current detecting unit 12 respectively detect the voltage and the current generated in the linear compressor 13 and respectively output it to the microcomputer 15.
The microcomputer 15 calculates a stroke by using the voltage and the current detected from the voltage detecting unit 14 and the current detecting unit 12, compares the calculated stroke with the stroke reference value and outputs a switching control signal according to it. In more detail, when the calculated stroke is smaller than the stroke reference value, the microcomputer 15 outputs a switching control signal for lengthening on cycle of the triac TrI to the power supplying unit 11 in order to increase a stroke voltage supplied to the linear compressor 13.
On the contrary, when the calculated stroke is larger than the stroke reference value, the microcomputer 15 outputs a switching control signal for shortening on cycle of the triac TrI to the power supplying unit 11 in order to decrease a stroke voltage supplied to the linear compressor 13.
However, in the linear compressor in accordance with the present invention, because the operation of the linear compressor is controlled by comparing the calculated stroke with the stroke reference value and outputting a switching control signal according to it to the power supplying unit, it is impossible to control the operation of the linear compressor accurately. In more detail, because the reciprocating compressor in accordance with the prior art has a serious nonlinearity in the mechanical motion characteristic aspect, it is impossible to perform a precise control of the linear compressor with a control method not considering the nonlinearity.
Accordingly, it is an object of the present invention to provide an apparatus and a method for controlling operation of a compressor which is capable of controlling operation of a linear compressor precisely and accurately by detecting an inflection point on the basis of a current and a voltage generated in the linear compressor and generating a switching control signal on the basis of the inflection point.
In order to achieve the above-mentioned object, an apparatus for controlling operation of a compressor in accordance with the present invention includes a displacement calculating unit calculating a displacement by using a current and a voltage generated in a compressor, a detecting unit detecting a vector magnitude and a phase signal on the basis of a maximum current vector and a maximum displacement vector having a trace corresponded to the current and the displacement, an inflection point detecting unit detecting a vector magnitude inflection point on the basis of the vector magnitude and a previous detected vector magnitude and a phase inflection point on the basis of the phase signal and a previous detected phase signal, and a duty ratio determining unit controlling the operation of the compressor by comparing the vector magnitude inflection point with the phase inflection point and generating a switching control signal according to it.
In order to achieve the above-mentioned object, a method for controlling operation of a compressor in accordance with the present invention includes calculating a displacement by using a current and a voltage generated in a compressor, detecting a vector magnitude and a phase signal on the basis of a maximum current vector and a maximum displacement vector having a trace corresponded to the current and the displacement, detecting a vector magnitude inflection point on the basis of the vector magnitude and the previous detected vector magnitude and a phase inflection point on the basis of the phase signal and the previous detected phase signal, and controlling the operation of the compressor according to a switching control signal by comparing the vector magnitude inflection point with the phase inflection point and generating the switching control signal according to it.